#include <stdio.h>
#include <stdlib.h>
#define N 100000
#define L 16 /* L = floor(log2(N)) */
#define INF 0x3f3f3f3f3f3f3f3fLL
long long min(long long a, long long b) { return a < b ? a : b; }
int ii[N - 1], jj[N - 1], ww[N - 1];
int *oh[N], oo[N];
void append(int i, int h) {
int o = oo[i]++;
if (o >= 2 && (o & o - 1) == 0)
oh[i] = (int *) realloc(oh[i], o * 2 * sizeof *oh[i]);
oh[i][o] = h;
}
char shop[N]; int dd[N], pp[N][L + 1]; long long xx[N], xx_[N], yy[N][L + 1];
void dfs1(int p, int i, int d, long long x) {
int o, l;
dd[i] = d, xx[i] = x, xx_[i] = shop[i] ? x : INF;
pp[i][0] = p;
for (l = 1; 1 << l <= d; l++)
pp[i][l] = pp[pp[i][l - 1]][l - 1];
for (o = oo[i]; o--; ) {
int h = oh[i][o], j = i ^ ii[h] ^ jj[h];
if (j != p) {
ii[h] = i, jj[h] = j, dfs1(i, j, d + 1, x + ww[h]);
xx_[i] = min(xx_[i], xx_[j]);
}
}
}
void dfs2(int p, int i) {
int o, l;
yy[i][0] = xx_[i] == INF ? INF : xx_[i] - xx[i] * 2;
for (l = 1; 1 << l <= dd[i]; l++)
yy[i][l] = min(yy[i][l - 1], yy[pp[i][l - 1]][l - 1]);
for (o = oo[i]; o--; ) {
int h = oh[i][o], j = i ^ ii[h] ^ jj[h];
if (j != p)
dfs2(i, j);
}
}
long long query(int i, int j) {
int i_, l;
long long y;
if (dd[i] < dd[j])
return -1;
y = INF;
for (i_ = i, l = L; l >= 0; l--)
if (1 << l <= dd[i_] - dd[j])
y = min(y, yy[i_][l]), i_ = pp[i_][l];
if (i_ != j)
return -1;
y = min(y, yy[i_][0]);
return y == INF ? INF : y + xx[i];
}
int main() {
int n, k, q, r, h, i, j;
scanf("%d%d%d%d", &n, &k, &q, &r), r--;
for (i = 0; i < n; i++)
oh[i] = (int *) malloc(2 * sizeof *oh[i]);
for (h = 0; h < n - 1; h++) {
int w;
scanf("%d%d%d", &i, &j, &w), i--, j--;
ii[h] = i, jj[h] = j, ww[h] = w;
append(i, h), append(j, h);
}
while (k--) {
scanf("%d", &i), i--;
shop[i] = 1;
}
dfs1(-1, r, 0, 0);
dfs2(-1, r);
while (q--) {
long long ans;
scanf("%d%d", &h, &i), h--, i--;
ans = query(i, jj[h]);
if (ans == -1)
printf("escaped\n");
else if (ans == INF)
printf("oo\n");
else
printf("%lld\n", ans);
}
return 0;
}
